Art of cracking hydrocarbons



May 24, 1932.

' E. C, HERTHEL ART OF CRACKING HYDROCARBONS Filed* Dec. 1e, 1929 lNvENToR fige/1e 6 Her/e7 BY ZM;

ATTORNEYS Patented May 24, 1932 l UNITEDl STATES :EU-'GENE C. HEB/THEL, OF FI'OSSMOOR, ILLINOIS, ASSIGNOR TO SINCLAIR REFINING COMPANY, OFNEW YORK, N. Y., A. CORPORATION 0F MAINE ART 0F CRACKING HYDROCARBONS Application led December 16, 1929. Serial No. 414,419.

This invention relates to improvements in the manufacture of gasoline by cracking operations producing a mixture including a gasoline condensate and a large volume of hydrocarbon gases and vapors; the invention relates, more particularly, to the separation and recovery of gasoline condensates from such mixtures..

The invention is of special value in conjunction With vapor phase cracking opera.- tions, such, for example, as are described in an application filed June 13th, 1927, Serial Number 198,621, by Harry LfPelzer, but the invention is also useful in conjunction with other types of cracking operations producing a large volume of hydrocarbon gases and vapors together with the gasoline condensate from which the gasoline condensate must be separated.

In conventional pressure distillation cracking operations in which the oil undergoing pressure distillation is heated to a cracking temperature in the general range of 775-85()o F., the gas-vapor mixture produced, incondensable at ordinary atmospheric temperatures and pressures, may approximate in` volume, for example, 7-15 cubic feet per gallon of the gasoline condensate produced.

In vapor phase cracking operations, as currently practiced, the gas-vapor mixture produced may approximate in volume, by Way of contrast, for example, -90 cubic feet per gallon of the gasoline condensate produced. The foregoing gures are not inclusive of all operations of either class, but they represent fairly the enormously increased production of gases and vapors incondensable at ordi'- nary atmospheric temperatures and pressures usually encountered in vapor phase cracking operations as compared with pressure distillation cracking operations. This increased production of such gases and vapors involves a number of peculiar problems.

Conditions "of temperature and pressure remaining the same, two units of volume of such a gas-vapor mixture require for saturation the presence of twice as much of any eondensable vapor as one unit of volume. As a consequence, this increased production of gas and vapor incondensableat ordinary atmospheric temperatures and pressures tends to involve a correspondingly increased loss of gasoline constituents required to saturate the gas-vapor mixture. In conventional practice, separation of the gas-vapor mixture from the gasoline condensate in a receiver, or successive receivers, following a condenser, this loss corresponds approximately to the volume of the'gas-vapor mixture produced.

Loss of eondensable constituents of the gasoline condensate through the operation of this property of such gas-vapor mixtures is, of course, encountered in conventional pressure distillation cracking operations, for example, and a number of expedients have been adopted to avoid or minimize this loss. For example, following separation of the gasoline condensate and the gas-vapor mixture, the gas-vapor mixture has been subjected to scrubbing operations with various scrubbing media Jfrom which scrubbing media absorbed eondensable constituents have been subsequently recovered. It Will be apparent that this scheme involves a number of difficulties in application tooperations in which the volume of the gas-vapor mixture is increased, for example, ten times.

It has also been proposed to compress together the gasoline condensate and the large volume of gases and vapors produced by severe cracking operations to absorb in the gasoline condensate itself eondensable constituents entrained in the gases and vapors, but in practical operation, even though an improved equilibrium is obtained under the imposed pressure, much the same loss is encountered When the pressure on the gasoline conldensate is'subsequently reduced to nor-v ma This invention provides an improved method for separating the gasoline condensate trom such condensate-gas-vapor mixtures with a high ultimate recovery of eondensable constituents in the separated gasoline condensate, with a low inclusion of non-gasoline constituents in the separated gasoline condensate, and with a 10W loss of eondensable gasoline constituents in the separated gas mixtures.

In carrying out the present invel1t,i 01.1,.ther

gasoline condensate is initially .separated from the uncondensed vapors and gases under relatively low pressure, in the conventional' receiver for example, the separated 5 gases and vapors are then compressed and `the compressed jected to a scru bing operation with the initially separated gasoline condensate under relatively high pressure, the ,scrubbed gas mixture and the condensate mixture including absorbed constituents are separately taken oil from the lscrubbing operation, the condensate mixture from the scrubbing operation is subjected toa rectifying operatlon under relatively high pressure rand a gas mixture and a'rectified gasoline condensate are separately taken off from therectifying operation, and the pressure on the rectified condensate is reduced to normal.

The mixturel of uncondensed vapors and gases initially separated from the gasoline condensate includes a substantial proportion of gasoline constituents, and the initially separated gasolinel condensate may similarly include a substantial proportion of constituents condensable at ordinary atmospheric temperatureand pressure but dissolved or otherwise .entrained in the separated condensate. Under the high pressure prevailingv in the scrubbing operation, the

gas mixture is stripped of condensable gasoline constituents. The resulting condensate mixture, however, includes a substantial proortion of constituents incondensable at orinary atmospheric temperature and pressure. In the following rectifying operation, this condensate mixture is accurately fractionated to produce a inal gasoline condensate including a maximum of condensable constituents yet free from any such proportion of constituents incondensable at ordinary atmospheric temperatures and pressures as would involve, under `normal conditions, excessivefevaporation losses from the condensate. A high ultimate recovery of a stable gasoline condensate is thus obtained.

' The invention will be further described in connection with the accompanying drawings, which illustrate, diagrammatically and conventionally, one form of apparatus adapted for carrying out the process of the invention.

Referring to the drawings, the" apparatus illustrated comprises a receiver 1, a compressor 2, a pump 3, a scrubbing tower 4 and a` rectifying tower 5. f

The receiver 1 is connected to the condenser of the apparatus in which the cracking .operation is carried out, in which the 0 gasoline vapors produced are condensed, through connection 6. For example, the receiver 1 may correspond to the receiver 93 connected to the condenser 84 in the apparatus illustrated in application Serial Number 198,621, mentioned above.

gases and vapors are sub.

The scrubbing tower ldemay be of any con- -ventionalt pe provided with means for prometing intlmate contact between down flowing liquid and up flowing vapors and gases. The recti-fying tower 5 may be of any 4conventional type, for example, it may consist of an appropriate number of bubble sections.l The rectifying tower 5 is shown as provided with a cooling coil 7 and a heating coil 8 for purposes'ot` control.

In carrying out the invention in the apparatus illustrated, the condensate-gas-vapor mixture from the cracking operation is discharged into the receiver 1 through connection 6. An initial separa-tion of condensate from uncondensed vapors and gases is effected in this receiver. The receiver may be operated, for example, with a pressure approximating 0-35 pounds per square inch. The condensate separated in the receiver 1 is pumped through connections 9 and 10 by means of pump 3 into the upperend of the scrubbing tower 4, and the gas mixture separated in receiver 1 is forced into the lower end `of scrubbing tower 4 through connections 11 and 12 by means of compressor 2. The scrubbing tower 4 may be operated, lfor example, under a pressure approximating 200-300 pounds per square inch.v The stripped gas mixture is discharged from the upper end of the scrubbing tower 4 through connection 13.

The condensate mixture including constitu ents absorbed from the gas mixture in the scrubbing tower 4 is discharged through connection 14 to the rectifying tower 5. The rectifying tower 5 may be operated underv a pressure approximating that prevailing in the scrubbing tower 4. A gas mixture substantially free from condensable gasoline yconstituents is discharged from the upper.

end of the rectifying tower 5 through connection 15. The rectified gasoline condensate is discharged from the lower end of the rectify-A bing tower 4. These unsaturated hydrocar-l bons may then be recovered as constituents of the gas mixture separated in the rectifying tower 5 in concentration suicient to perl mit their utilization in the manufacture of synthetic alcohols. A compounded alcohol product may be so produced from this gas mixture, b v conventional methods, and incorporated in the gasoline condensate where it is intended for use as motor fuel.

Relatively lower pressure may be used in the scrubbing tower 4 if no recovery of such very low boiling unsaturated hydrocarbons is desired.

I claim:

ln the manufacture of gasoline by cracking voperations producing a mixture including a gasoline condensate and a large volume of hydrocarbon gases and vapors, the improve- Ament which. comprises effecting .an initial separation-of the condensate and the gases and vapors under relatively low pressure,`

compressing the separated gases and va ors and subjectin the compressed gases an vapors to a scru bing operation with the separated condensate under relatively high pressure, taking oiif a scrubbed gas mixture from the scrubbing operation, separately taking 01T a condensate mixture including absorbed constituents from the scrubbing operationA and subjecting this condensate mixture to a rectiying operation under relatively high pressure, taking off a gas mixture from the vrectifying operation, and taking ofi' from the rectifying operation and reducing to normal the pressure on a rectified gasoline condensate.

In testimony whereof I aiix my signatureA EUGENE C. HERTHEL.. 

